Remove CSSCustomState flags

This patch removes flags for the rename from :--foo to :state(foo) now
that the enterprise policy for the old behavior has been around long
enough and can be removed.

Bug: 41486953
Fixed: 381362594, 381384409
Change-Id: Iac29106278ffa0a4844f801be014707ec9732604
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6064427
Reviewed-by: Salma Elmahallawy <esalma@google.com>
Commit-Queue: Joey Arhar <jarhar@chromium.org>
Reviewed-by: Mason Freed <masonf@chromium.org>
Reviewed-by: Yann Dago <ydago@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1393048}